Motorcycle tire

ABSTRACT

Provided is a motorcycle tire whose wear resistance and drainage performance are improved by refining the tread pattern. 
     The motorcycle tire includes: a tread section; and side wall sections and bead sections that continuously extend on both sides of the tread section, and the rotation direction of the motorcycle tire when fitted to a motorcycle is designated. In a tread section  10 , first inclined main grooves  1  of a linear or curved shape which are inclined with respect to the tire circumferential direction, second inclined main grooves  2  of a linear or curved shape which are inclined in the same direction as the first inclined main grooves  1  but at a different angle, and shallow grooves  3  which are inclined in a different direction from the first inclined main grooves  1  and the second inclined main grooves  2  with respect to the tire circumferential direction are arranged, and the shallow grooves  3  are arranged only in a shoulder part.

TECHNICAL FIELD

The present invention relates to a motorcycle tire (hereinafter, alsosimply referred to as “tire”). More particularly, the present inventionrelates to a motorcycle tire whose wear resistance and drainageperformance are improved by refining the tread pattern.

BACKGROUND ART

Because of the characteristic of two-wheeled vehicles to make turns bytilting the body, which is different from four-wheeled vehicles such aspassenger cars and trucks, motorcycle tires have a shape in which thecrown section has a smaller curvature and a rounder cross-section thanfour-wheeled vehicle tires. Therefore, depending on the position of theground-contacting portion in a ground contact state, the slipping partsin the ground-contacting surface may be uneven particularly when a largedriving force is applied, and this is likely to cause uneven wear inwhich specific parts are rapidly worn out. In such motorcycle tires, avariety of tread patterns are formed by adopting plural combinations ofthe number and the shape of grooves arranged in the tire tread sectionso as to improve various tire performances, such as drainage performancein wet conditions and wear resistance.

For instance, Patent Document 1 proposes a motorcycle tire in whichthermal degradation of the tread section can be inhibited whilemaintaining the turning performance and serviceable life (wearresistance) of the tire. In this tire proposed in Patent Document 1, theangle and pitch of the inner-side inclined main grooves arranged atprescribed positions, the inclined narrow grooves arranged betweenadjacent inner-side inclined main grooves, and the land ratio of thesurface in contact with the ground in straight running are adjusted.Further, Patent Document 1 also discloses that the drainage performancecan be further improved by adjusting, for example, the land ratio of thetread section, the arrangement pitch of the inner-side inclined maingrooves, and the width of the inner-side inclined main grooves.

RELATED ART DOCUMENT Patent Document

-   Patent Document 1: Japanese Unexamined Patent Application    Publication No. 2013-180664

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Generally speaking, for improvement of the wear resistance of a tire, itis effective to increase the land portion of the tread section; however,the groove ratio in the tread section decreases as the land portion isincreased. This makes it difficult to maintain the drainage performance,and it is thus extremely difficult to satisfy both wear resistance anddrainage performance. The tire proposed in Patent Document 1 also hasthese problems and cannot sufficiently comply with the demands ofsatisfying both wear resistance and drainage performance; therefore, afurther improvement in these properties is desired.

In view of the above, an object of the present invention is to provide amotorcycle tire whose wear resistance and drainage performance areimproved by refining the tread pattern.

Means for Solving the Problems

The present inventors intensively studied to solve the above-describedproblems and consequently discovered that, by allowing inclined maingrooves arranged in the tread section to have a prescribed inclinationangle and allowing shallow grooves to have a prescribed inclinationdirection, the wear resistance and the drainage performance can befurther improved and the problems can be solved as a result, therebycompleting the present invention.

That is, the motorcycle tire of the present invention is a motorcycletire which comprises: a tread section; and side wall sections and beadsections that continuously extend on both sides of the tread section,and whose rotation direction when fitted to a motorcycle is designated,the motorcycle tire being characterized in that:

in the tread section, first inclined main grooves of a linear or curvedshape which are inclined with respect to the tire circumferentialdirection, second inclined main grooves of a linear or curved shapewhich are inclined in the same direction as the first inclined maingrooves but at a different angle, and shallow grooves which are inclinedin a different direction from the first inclined main grooves and thesecond inclined main grooves with respect to the tire circumferentialdirection are arranged; and

the shallow grooves are arranged only in a shoulder part.

In the tire of the present invention, it is preferred that the firstinclined main grooves and the second inclined main grooves intersectwith the shallow grooves. In the tire of the present invention, it isalso preferred that the first inclined main grooves and the shallowgrooves intersect with each other on the tire width direction outer siderelative to the midpoints of the first inclined main grooves in the tirewidth direction; and that the second inclined main grooves and theshallow grooves intersect with each other on the tire width directionouter side relative to the midpoints of the second inclined main groovesin the tire width direction. Further, in the tire of the presentinvention, it is preferred that the shallow grooves extend to the tirewidth direction outer side relative to the tire width direction outerends of the second inclined main grooves. Still further, in the tire ofthe present invention, it is preferred that the shallow grooves have adepth of 0.1 to 0.5 mm. The tire of the present invention can besuitably used as a front tire of a motorcycle.

Effects of the Invention

According to the present invention, a motorcycle tire whose wearresistance and drainage performance are improved by refining the treadpattern can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is one example of a partial development view illustrating thetread section of a motorcycle tire according to one preferred embodimentof the present invention.

FIG. 2 is one example of a cross-sectional view taken along the widthdirection of a motorcycle tire according to one preferred embodiment ofthe present invention.

MODE FOR CARRYING OUT THE INVENTION

The motorcycle tire of the present invention will now be described indetail referring to the drawings.

The motorcycle tire of the present invention is a motorcycle tire whichcomprises: a tread section; and side wall sections and bead sectionsthat continuously extend on both sides of the tread section, and whoserotation direction when fitted to a motorcycle is designated, and themotorcycle tire of the present invention exerts its effects mostprominently when used as a front tire. FIG. 1 is one example of apartial development view illustrating the tread section of a motorcycletire according to one preferred embodiment of the present invention, andthe arrow drawn therein represents the rotation direction of the tire.

As illustrated in FIG. 1, in the tire of the present invention, firstinclined main grooves 1, which are inclined with respect to the tirecircumferential direction, and second inclined main grooves 2, which areinclined in the same direction as the first inclined main grooves 1 butat a different angle, are arranged in a tread section 10. In theillustrated example, the first inclined main grooves 1 are arranged toextend from a central part to a shoulder part, and the second inclinedmain grooves 2 are arranged in the shoulder part. It is noted here thatthe term “central part” used herein refers to a region of the treadsection 10 that comes into contact with the road surface when the tireis filled with air at a normal inner pressure, a normal load was appliedthereto and a motorcycle fitted with the tire is put in a standingposition, and the term “shoulder part” used herein refers to the regionsof the tread section 10 on both sides of the central part. The inclinedmain grooves can each have a depth of, for example, 3 to 6 mm at thedeepest point.

In the tire of the present invention, the drainage performance isensured by the first inclined main grooves 1 and the second maininclined grooves 2, and it is preferred that the first inclined maingrooves 1 and the second main inclined grooves 2 both have a linearshape or a curved shape. In the illustrated example, the first inclinedmain grooves 1 and the second main inclined grooves 2 both have a curvedshape. The reason for this is because smooth drainage is inhibited whenthe inclined main grooves have a bending point and, in order to preventthis, in the tire of the present invention, the inclined main groovesare formed in a linear or curved shape with no bending point.

Further, in the tire of the present invention, as illustrated in FIG. 1,shallow grooves 3 (three of them in the illustrated example), which areinclined in a different direction from the first inclined main grooves 1and the second main inclined grooves 2, are arranged. The drainageperformance can be further improved by the shallow grooves 3. Theshallow grooves 3 refer to grooves having a depth of 10% or less withrespect to the depth of the respective first inclined main grooves 1 andsecond inclined main grooves 2. Brand-new tires are slippery due to thepresence of silicon used in the tire vulcanization process on theirsurface layers. In addition, it is not preferable to arrange a largenumber of main grooves in the shoulder part. Therefore, in the tire ofthe present invention, the initial drainage performance of the shoulderpart is improved by arranging the shallow grooves 3 in the shoulderpart. Since the rigidity of the central part may be reduced and the wearresistance may thus be deteriorated by arranging the shallow grooves 3in the central part, in the tire of the present invention, the shallowgrooves 3 are arranged only in the shoulder part. In the tire of thepresent invention, by allowing the shallow grooves 3 to have a depth of0.1 to 0.5 mm, the drainage performance can be favorably improved whilemaintaining the rigidity of the tread section.

Further, as described above, the tire of the present invention issuitably used as a front tire, and the inputs to the front tire arebraking force and lateral force. Therefore, in order to allow the tireto effectively exert a turning force, it is preferred to arrange groovesin a direction that interferes with the inputs as little as possible,that is, in the direction along the inputs. From this standpoint, it ispreferred that the first inclined main grooves 1 and the second maininclined grooves 2 are all configured in a curved shape whose center ofthe radius of curvature is on the reverse rotation side of thedesignated tire rotation direction, that is, on the trailing side withrespect to the running direction. Moreover, the angle of the shallowgrooves 3 is preferably aligned with the normal direction with respectto the direction along the inputs.

In the illustrated example, the first inclined main grooves 1 and thesecond main inclined grooves 2 are in communication with the shallowgrooves 3; however, the tire of the present invention may also take aconfiguration in which the first inclined main grooves 1 and the secondmain inclined grooves 2 are not in communication with the shallowgrooves 3 and the shallow grooves 3 are arranged between and withoutintersecting with the respective first inclined main grooves 1 andsecond inclined main grooves 2. Preferably, the shallow grooves 3 arearranged in such a manner to intersect with the first inclined maingrooves 1 and the second main inclined grooves 2. This allows waterflowing along the shallow grooves to flow into the inclined main groovesand to be drained from the inclined main grooves, so that the drainageperformance can be further improved.

In the tire of the present invention, it is also preferred that thefirst inclined main grooves 1 and the shallow grooves 3 intersect witheach other on the tire width direction outer side relative to themidpoint C1 of each first inclined main groove 1 in the tire widthdirection; and that the second inclined main grooves 2 and the shallowgrooves 3 intersect with each other on the tire width direction outerside relative to the midpoint C2 of each second inclined main groove 2in the tire width direction. As described above, the shallow grooves 3are required to be arranged in the shoulder part. In addition, it ispreferred that the shallow grooves 3 intersect with the first inclinedmain grooves 1 and the second inclined main grooves 2. Theserequirements can be simultaneously satisfied by arranging the shallowgrooves 3 in the above-described manner. Moreover, since the groundcontact-leading parts of the first inclined main grooves 1 and those ofthe second inclined main grooves 2 are on the shoulder side, drainagecan start at the moment when these parts come into contact with theground. Taking into consideration the drainage effect of the shoulderpart, the shallow grooves 3 preferably extend to the tire widthdirection outer side relative to the tire width direction outer ends ofthe second inclined main grooves 2.

Further, in the tire of the present invention, it is preferred that thepart of each first inclined main groove 1 where the distance between thegroove walls in the tire circumferential direction is the maximum W1exists on the inner side relative to the midpoint C1 of the firstinclined main groove 1 in the tire width direction; and that the part ofeach second inclined main groove 2 where the distance between the groovewalls in the tire circumferential direction is the maximum W2 exists onthe outer side relative to the midpoint C2 of the second inclined maingroove 2 in the tire width direction. That is, the first inclined maingrooves 1 are thicker on the tire width direction inner side, while thesecond inclined main grooves 2 are thicker on the tire width directionouter side. In the illustrated example, the width of each first inclinedmain groove 1 gradually decreases toward the outer side in the tirewidth direction, while the width of each second inclined main groove 2decreases toward the inner side in the tire width direction.

By making the first inclined main grooves 1 thicker on the tire widthdirection inner side in this manner, the drainage performance of thecentral part can be improved, which is effective for inhibiting thehydroplaning phenomenon during high-speed travel. Moreover, by makingthe second inclined main grooves 2 thicker on the tire width directionouter side, excessive pattern rigidity of the shoulder part can bereduced, so that the wear resistance of the shoulder part can beimproved. In order to favorably obtain these effects, the part of eachfirst inclined main groove 1 where the distance between the groove wallsin the tire circumferential direction is the maximum is preferably thetire width direction inner end 1 a of the groove wall on therotation-direction leading side of the first inclined main groove 1, andthe part of each second inclined main groove 2 where the distancebetween the groove walls in the tire circumferential direction is themaximum is preferably the tire width direction outer end 2 a of thegroove wall on the rotation-direction trailing side of the secondinclined main groove 2.

Still further, in the tire of the present invention, it is preferredthat the first inclined main grooves 1 extend over the tire equator CL.By arranging the first inclined main grooves 1 across the equator CL,the pattern rigidity along the equator CL can be reduced, and thisconsequently enables to perform steering with a small force. In theillustrated example, the second inclined main grooves 2 do not extend tothe central part. The reason for this is because, when the secondinclined main grooves 2 extend to the central part, the rigidity of thecentral part is excessively reduced, and this may lead to deteriorationof the wear resistance of the central part.

In the illustrated example, the tire width direction outer ends of thesecond inclined main grooves 2 are on the outer side relative to thetire width direction outer ends of the first inclined main grooves 1.The reason for this is because, in motorcycles, since turns are made bytilting the motorcycle body at the time of cornering, the shoulder partof the tire comes into contact with the road surface and, when the firstinclined main grooves 1 extend to the tire width direction outer side ofthe tread section 10 further than the second inclined main grooves 2,the shoulder part does not have sufficient rigidity and the corneringperformance may thus be impaired. It is noted here that, although thefirst inclined main grooves 1 are longer than the second inclined maingrooves 2, the tire of the present invention is not restricted to thisconfiguration.

Yet still further, in the tire of the present invention, it is preferredthat the second inclined main grooves 2 at least partially overlap withthe first inclined main grooves 1 in the tire circumferential direction,and the tire width direction length of the region where the firstinclined main grooves 1 and the second inclined main grooves 2 overlapwith each other (overlapping length L) is preferably 30 to 60% of thelength of the first inclined main grooves 1 in the tire circumferentialdirection. It is noted here that the overlapping length L is theprojected length of each inclined main groove in the tire widthdirection, not the length along each inclined main groove. Thisconfiguration enables to set an appropriate distance between therespective first inclined main grooves 1 and second inclined maingrooves 2.

That is, when the overlapping length L is greater than 60%, the secondinclined main grooves 2 are close to each first inclined main groove 1on the rotation-direction leading side of the tire and the negativedistribution in the width direction is thus uneven (the negative ratiois locally small in the central part or the shoulder part), making itdifficult to attain stable wet performance as the camber angle isincreased. Meanwhile, when the overlapping length L is less than 30% aswell, since the negative ratio is locally small in the treadintermediate region, it is after all difficult to attain stable wetperformance as the camber angle is increased.

Furthermore, in the tire of the present invention, it is preferred thatthe second inclined main grooves 2 are more inclined than the firstinclined main grooves 1 with respect to the tire circumferentialdirection. In motorcycles, since turns are made by tilting themotorcycle body at the time of cornering, the shoulder part of the tirecomes into contact with the road surface. Accordingly, during cornering,a force is applied to the shoulder part in a direction close to the tirewidth direction. Therefore, when the angle of the second inclined maingrooves 2 in the shoulder part is close to the tire circumferentialdirection, the shoulder part is excessively deformed and the drivingstability during cornering is thereby reduced. In the tire of thepresent invention, the angle of the first inclined main grooves 1 withrespect to the tire circumferential direction is preferably 20 to 40°,and the angle of the second inclined main grooves 2 with respect to thetire circumferential direction is preferably 40 to 70°. It is noted herethat the angle of the first inclined main grooves 1 and that of thesecond inclined main grooves 2 each refer to an angle formed by a lineconnecting the centers of the tire width direction ends of therespective grooves and the tire circumferential direction.

In the tire of the present invention, as long as the relationships ofthe shallow grooves, the first inclined main grooves and the secondinclined main grooves satisfy the above-described requirements, there isno other particular restriction. For instance, the shallow grooves 3illustrated in FIG. 1 play an auxiliary role of the first inclined maingrooves 1 and the second inclined main grooves 2 during drainage;however, the shape of the shallow grooves 3 is not particularlyrestricted. In the illustrated example, the shallow grooves 3 are threegrooves that are inclined in the opposite direction of the firstinclined main grooves 1 and the second inclined main grooves 2 and havea shape in which both ends of each groove are closed; however, theconfiguration of the shallow grooves 3 is not restricted thereto. Forinstance, the shallow grooves 3 may be in the form of a single straightline or a curve line.

FIG. 2 is one example of a cross-sectional view taken along the widthdirection of a motorcycle tire according to one preferred embodiment ofthe present invention. As illustrated in FIG. 2, a tire 100 of thepresent invention comprises: a tread section 101; a pair of side wallsections 102, which continuously extend on both sides of the treadsection 101; a pair of bead sections 103, which continuously extend fromeach of the pair of the side wall sections 102; and a carcass 104, whichis composed of at least one carcass ply layer (one carcass ply layers inthe illustrated example) reinforcing the above-described sections overthe range between the bead sections 103. In the illustrated example,both ends of the carcass 104 are folded around a bead core 105 from theinside to the outside of the tire to be anchored; however, the ends ofthe carcass 104 may each be sandwiched and anchored by a bead wire.

Further, in the tire illustrated in FIG. 2, a belt layer 106 is arrangedon the tire radial direction outer side of the carcass 104. The beltcord of the belt layer 106 is also not particularly restricted, and anyknown non-extensible high-elasticity cord can be used. For example, anaromatic aramid cord or a steel cord can be suitably used. In the tire100 illustrated in FIG. 2, a spiral belt layer 107 is further arrangedon the tire radial direction outer side of the belt layer 106. Thisspiral belt layer 107 is formed by spirally winding in thecircumferential direction an elongated rubber-coated cord obtained bycoating a single cord with rubber or a strip-form ply obtained bycoating a plurality of cords with rubber, and the cord(s) can beselected as appropriate from, for example, steel cords, cords made oforganic fibers such as aramid (e.g., trade name “Kevlar®” manufacturedby DuPont), polyethylene naphthalate (PEN), polyethylene terephthalate(PET), rayon or nylon, and cords made of a material such as glass fiberor carbon fiber.

EXAMPLES

The present invention will now be described in more detail by way ofexamples thereof.

Example 1

A motorcycle tire having a tread pattern of the type illustrated in FIG.1 was produced at a size of 120/70ZR17M/C. The first inclined maingrooves had a shape of being thick on the tire width direction innerside and gradually getting narrower toward the tire width directionouter side, and the second inclined main grooves had a shape of beingthick on the tire width direction outer side and gradually gettingnarrower toward the tire width direction inner side. The shallow grooveshad an angle of 20° with respect to the tire circumferential direction,and the points of intersection between the shallow grooves and the firstand second inclined main grooves were positioned on the tire widthdirection outer side by more than ½ of the length of each inclined maingroove in the tire width direction. The shallow grooves had a depth of0.3 mm and were arranged only in the shoulder part.

The maximum distance between the groove walls of each first inclinedmain groove was set at 14 mm, and the position of this maximum distancebetween the groove walls of each first inclined main groove was the tirewidth direction inner end of the groove wall on the rotation directionleading side of the first inclined main groove. Further, the maximumdistance between the groove walls of each second inclined main groovewas set at 7 mm. The position of this maximum distance between thegroove walls of each second inclined main groove was the tire widthdirection outer end of the groove wall on the rotation directiontrailing side of the second inclined main groove. Moreover, the firstinclined main grooves were arranged across the tire equator, and theoverlapping length L of the first and second inclined main grooves was45%. The first inclined main grooves had an angle of 30° with respect tothe tire circumferential direction, and the second inclined main grooveshad an angle of 55° with respect to the tire circumferential direction.

Example 2

The motorcycle tire of Example 2 was produced in the same manner as inExample 1, except that the shallow grooves did not extend to the tirewidth direction outer side of the second inclined main grooves.

Example 3

The motorcycle tire of Example 3 was produced in the same manner as inExample 1, except that the shallow grooves intersected with neither thefirst inclined main grooves nor the second inclined main grooves.

Example 4

The motorcycle tire of Example 4 was produced in the same manner as inExample 1, except that the shallow grooves had a depth of 1.0 mm.

Example 5

The motorcycle tire of Example 5 was produced in the same manner as inExample 1, except that the points of intersection between the shallowgrooves and the first and second inclined main grooves were positionedat a distance of ⅗ or greater of the length of the respective first andsecond inclined main grooves from their width direction outer ends.

Comparative Example 1

The motorcycle tire of Comparative Example 1 was produced in the samemanner as in Example 1, except that the shallow grooves were inclined inthe same direction as the first and second inclined main grooves.

Comparative Example 2

The motorcycle tire of Comparative Example 2 was produced in the samemanner as in Example 1, except that the shallow grooves extended to thecentral part.

The thus obtained tires were each assembled to a wheel having a rim sizeof MT3.5×17 inches and fitted to a 1,000-cc motorcycle as the front tireat an inner pressure of 250 kPa. As the rear tire, a conventional tirewas fitted. This rear tire had a size of 190/55ZR17M/C, a rim size ofMT6.0×17 inches and an inner pressure of 290 kPa. This motorcycle wasdriven on a test track, and the drainage performance of the front tireon wet road and the tire wear resistance were evaluated by the followingmethods.

<Wear Resistance of Central Part>

After the completion of the driving test performed by a test rider, thewear amount of each tire was measured using a depth gauge and compared.The results thereof are shown as index values where a value of 100represents the wear amount of the tire of Comparative Example 1. Alarger value indicates superior wear resistance.

<Drainage Performance>

The strength of the gripping force of each tire on wet road and thechange in the gripping strength in response to tilting of the tire wereevaluated by the test rider based on the feeling. The results thereofare shown as index values where a value of 100 represents the tire ofComparative Example 1. A larger value indicates superior drainageperformance.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Match between theinclination ∘ ∘ ∘ ∘ direction of shallow grooves and the direction offirst and second inclined main grooves*¹ Extension of shallow grooves to∘ ∘ ∘ ∘ the central part*² Position of the points of less than ½ lessthan ½ less than ½ less than 1/2 intersection between shallow groovesand first and second inclined main grooves*³ Presence or absence ofextension ∘ x ∘ ∘ of shallow grooves to the tire width direction outerside of second inclined main grooves Presence or absence of ∘ ∘ x ∘intersection between shallow grooves and first and second inclined maingrooves Shallow groove depth (mm) 0.3 0.3 0.3 1.0 Wear resistance of thecentral part 100 100 100 95 (index) Drainage performance (index) 110 105105 110 *¹A symbol of “∘” was assigned when the inclination direction ofthe shallow grooves and that of the first and second inclined maingrooves were different, and a symbol of “x” was assigned when theseinclination directions were the same. *²A symbol of “∘” was assignedwhen the shallow grooves did not extend to the central part, and asymbol of “x” was assigned when the shallow grooves extended to thecentral part. *³Indicates the position of the points of intersectionbetween the shallow grooves and the inclined main grooves in terms ofthe ratio of the width-direction length of the respective inclined maingrooves from their tire width direction outer ends.

TABLE 2 Comparative Comparative Example 5 Example 1 Example 2 Matchbetween the inclination direction of ∘ x ∘ shallow grooves and thedirection of first and second inclined main grooves*¹ Extension ofshallow grooves to the central ∘ ∘ x part*² Position of the points ofintersection not less than ⅗ less than ½ less than ½ between shallowgrooves and first and second inclined main grooves*³ Presence or absenceof extension of ∘ ∘ ∘ shallow grooves to the tire width direction outerside of second inclined main grooves Presence or absence of intersection∘ ∘ ∘ between shallow grooves and first and second inclined main groovesShallow groove depth (mm) 0.3 0.3 0.3 Wear resistance of the centralpart (index) 100 100 85 Drainage performance (index) 105 100 110

From the above, it is seen that the tire of the present invention hasexcellent wear resistance and excellent drainage performance.

DESCRIPTION OF SYMBOLS

-   -   1: first inclined main groove    -   2: second inclined main groove    -   3: shallow groove    -   10: tread section    -   100: motorcycle tire (tire)    -   101: tread section    -   102: side wall section    -   103: bead section    -   104: carcass    -   105: bead core    -   106: belt layer    -   107: spiral belt layer

1. A motorcycle tire which comprises: a tread section; and side wallsections and bead sections that continuously extend on both sides ofsaid tread section, and whose rotation direction when fitted to amotorcycle is designated, wherein in said tread section, first inclinedmain grooves of a linear or curved shape which are inclined with respectto the tire circumferential direction, second inclined main grooves of alinear or curved shape which are inclined in the same direction as saidfirst inclined main grooves but at a different angle, and shallowgrooves which are inclined in a different direction from said firstinclined main grooves and said second inclined main grooves with respectto the tire circumferential direction are arranged, and said shallowgrooves are arranged only in a shoulder part.
 2. The motorcycle tireaccording to claim 1, wherein said first inclined main grooves and saidsecond inclined main grooves intersect with said shallow grooves.
 3. Themotorcycle tire according to claim 1, wherein said first inclined maingrooves and said shallow grooves intersect with each other on the tirewidth direction outer side relative to the midpoints of said firstinclined main grooves in the tire width direction, and said secondinclined main grooves and said shallow grooves intersect with each otheron the tire width direction outer side relative to the midpoints of saidsecond inclined main grooves in the tire width direction.
 4. Themotorcycle tire according to claim 1, wherein said shallow groovesextend to the tire width direction outer side relative to the tire widthdirection outer ends of said second inclined main grooves.
 5. Themotorcycle tire according to claim 1, wherein said shallow grooves havea depth of 0.1 to 0.5 mm.
 6. The motorcycle tire according to claim 1,which is used as a front tire.